India In Triangles – Shruthi Rao

The difference between the measurement on the ground using the steel chain and the distance calculated through triangulation was less than 10 centimetres—an astonishingly small error! This relentless focus on accuracy is what made the GTS’s maps inch-perfect! Lambton delivered on his promise to the authorities to produce highly precise maps. For instance, after triangulating up to Mangalore and completing his calculations, he discovered that the actual distance between Madras and Mangalore was a staggering 38 miles (61 kilometres) shorter than previously believed!

After his trial baseline in Bangalore, from which he triangulated to a second trial baseline in Srirangapatna, the GTS team under Lambton went on to measure eleven more baselines. Between 1802 and 1825, they established baselines at: Madras Bangalore Coimbatore Thanjavur Palayamkottai (Tirunelveli) Gooty Guntur Kumta (near Gokarna, Karnataka) Bidar Takarkheda (near Amaravati, Maharashtra) Sironj (Madhya Pradesh) After 1830, surveyors replaced Lambton’s steel chains with compensation bars, introduced by George Everest.

Using this new apparatus, several additional baselines were measured, and some older ones were re-measured. Baselines established after 1830 included: Calcutta Dehradun Sironj Bidar Sonakhoda (near Ramganj, West Bengal) Attock (Pakistan) Karachi (Pakistan) Vishakapatnam Bangalore Kanyakumari Do you live near any of these places where a baseline was measured? Remember Lambton’s ‘grand desire’—his ambition to measure the shape of the Earth? To achieve this, he planned a chain of triangles snaking up the central spine of India.

This network would allow him to calculate the distance between two latitudes, or, in other words, how much a degree of longitude measured at different points along that spine. This was the question that Teams Egg and Grapefruit had left unanswered: How much does the Earth curve at the tropics? To ‘draw’ that chain of north-south triangles, from the Bangalore baseline, Lambton and his team began triangulating southwards, extending their survey all the way to Kanyakumari. Once they reached the southern tip of the subcontinent, they returned to Bangalore and continued extending their chain of triangles northward, roughly along the same longitude.

Along the way, several chains of triangles branched off to the east and west. These chains of triangles were called the longitudinal series and included the Bombay Longitudinal, the Calcutta Longitudinal, the Sambalpur Longitudinal, the Kathiawar Longitudinal and others. LONGITUDINAL SERIES: A confusing term, since these measurements actually follow a latitude. However, they are called ‘longitudinal’ because they are used to determine degrees of longitude as the survey moves along a latitude.

Lambton was on his way from Hyderabad to Nagpur when he passed away in 1823 at Hinganghat, near Wardha in Maharashtra. It was up to his successor, Colonel George Everest, to complete what became known as the Great Arc of the Meridian. OceanofPDF.com Sir George Everest—even if you haven’t heard of him, there is no doubt you know his last name.

It’s ironic that his name has been immortalised by Mount Everest. There is no evidence whatsoever that the man had even seen the mountain.

Shruthi Rao (shruthi-rao.com) writes for children. Nearly twenty of her books, both fiction and nonfiction, have been published in India and the USA. If she wants to learn more about a topic, she writes about it. Originally from Bengaluru, Shruthi now lives in northern California and loves stories, trees, benches, desserts, science and long walks. Meera Iyer loves listening to, researching and writing about stories of people and places, buildings and streets. She volunteers with the Indian National Trust for Art and Cultural Heritage to help protect and celebrate Bengaluru’s history and heritage.

She loves coffee, dark chocolate and potsherds. OceanofPDF.com For Sandesh—S.R. For Almitra Patel, who first showed me the GTS Observatory in Kannur—M.I. OceanofPDF.com A STRANGE SIGHT It was a warm October morning in the year 1800. A young boy led his cow along country roads in Banaswadi, Bangalore, while his dog scampered a few metres ahead. Suddenly, the trio stumbled upon a very strange sight. The boy stared. The dog stared. Even the cow stared.

In a nearby field, men lugged wooden boxes and iron bars, planting them into the ground. Another group hauled out thick, heavy iron chains. Some other men peered into boxes and pointed towards distances for no purpose that the boy could fathom. Inspecting the instruments and quietly issuing orders, was a tall, well-built Englishman with reddish hair.

The boy scratched his head. What were they doing? Were they building something? Were they digging a well? Or was that … a weapon of some sort? He decided it was safest to make himself scarce. The boy had stumbled upon the beginnings of the Great Trigonometrical Survey of India, one of the largest and most impressive scientific feats in history.

The Great Trigonometrical Survey of India (GTS) was an ambitious project to carry out the survey of the Indian subcontinent with scientific precision. It began in 1802 and took nearly 100 years to complete. WHAT WAS THE POINT OF THIS SURVEY? By the late 1700s, the East India Company (EIC) had taken control over large parts of the Indian subcontinent. EAST INDIA COMPANY/EIC/THE BRITISH The East India Company (EIC) was an English (later British) trading company established in 1600 to conduct trade with South Asia, East Asia and Southeast Asia.

This is a short excerpt from the opening of “” by Unknown, quoted for review and introduction purposes. All rights belong to the copyright holders.

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• Language: English (en)

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